Abstract:

We developed a model to investigate the dielectric properties of the
BaTiO₃ − Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) solid solution, which is a relaxor ferroelectric and exhibits long range disorder. The model uses ab initio methods
to determine all polarization states for every atomic configuration of 2 x 2 x 2
supercells of BT-BZT. Each supercell is placed on a lattice with an Ising-like
interaction between neighboring cell polarizations. This method allows us to
consider long range disorder, which is not possible with ab initio methods
alone, and is required to properly understand relaxor ferroelectric materials.
We analyze the Monte Carlo data for a single lattice configuration using the
multiple histogram method, and develop a modified histogram technique to
combine data from multiple lattice configurations. Our calculated values of
dielectric constant, specific heat, and polarization agree reasonably well with
experiment.